* {
    margin: 0;
    padding: 0;
    list-style: none;
    text-decoration: none;
    font-family: 宋体;
}

.u-img {
    width: 730px;
    height: 454px;
    margin: 50px auto;
    position: relative;

}

.u-img:hover .btn {
    display: block;
}

.u-img .img li {
    position: absolute;
    left: 0;
    top: 0;
    display: none;
}

.u-img .u-num {
    position: absolute;
    bottom: 20px;
    left: 0;
    font-size: 0;
    text-align: center;
    width: 100%;
}

.u-img .u-num li {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background-color: dimgray;
    color: #fff;
    display: inline-block;
    text-align: center;
    line-height: 20px;
    font-size: 15px;
    cursor: pointer;
    margin: 0 2px;

}

.u-img .u-num li.sel {
    background-color: #f00;
}

.btn {
    position: absolute;
    top: 50%;
    width: 20px;
    height: 40px;
    background-color: rgba(105, 105, 105, 0.5);
    color: #fff;
    font-size: 25px;
    text-align: center;
    line-height: 40px;
    margin-top: -20px;
    display: none;
    cursor: pointer;

}

.left {
    left: 0px;
}

.right {
    right: 0px;
}

